Cantilever stiffness and curl tester



Nov. 18, 1958 J. J. PRESS CANTILEVER STIFFNESS AND CURL TESTER 3 Sheets-Sheet 1 Filed July 6,- 1955 Nov. 18, 1958 J. J. PRESS 2,860,510

CANTILEVER STIFFNESS AND CURL TESTER Filed. July 6, 1955 5 Sheets-Sheet 2 INVENTOR. J'flqt J P6555 Nov. 18, 1958 J. J. PRESS 2,860,510

CANTILEVER STIF'FNESS AND CURL TESTER Filed July 6, 1955 3 Sheets-Sheet 3 IIIIIIIII/II/I ///////I/ /I//////// l/II/I/II INVENTOR. Jncx .7. Fees:

United States Patent 2,860,510 CANTILEVER STIFFNESS AND CURL TESTER Jack J. Press, New York, N. Y.

Application July 6, 1955, Serial No. 520,383 10 Claims. (ems-159 (Granted under Title 35, U. S. Code (1952), sec. 266) The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This application is a continuation in part of my colagrsiging application, Serial No. 296,509, filed June 30,

This invention relates to improvements in fabric-test ing devices, and more particularly pertains to improvements in cantilever-type fabric bending-length and flexural-rigidity testers.

Determination of the quality of the finish of a fabric in qualitative terms presents a subjective reaction, a reaction that is indefinite, elusive, and incapable of resolution into terms permitting precise comparisons. Judgment of the quality of the finish of a fabric in terms of the evidence of the senses of an individual depends on time and place, seasons, fashions, and personal'and racial predilections, and constitutes, in essence, aesthetic ap-' preciation. However, since the evidence of the senses depends on the physical properties of the material, physical measurements can be of great value in providing data upon which to exercise judgment. The ultimate physical properties that can be used as measures of handle of a fabric and that can be included under thev generic nam stiffness include the following: h

(1) The bending length, c.-The manner in which a fabric drapes or hangs depends largely on its effective stiifness, which comprises resistance to bending and weight. The determination of the cube root of the ratio of these two quantities, expressed in suitable units, can beregarded as a quantitative measure of the propertyon which the hang of the fabric depends. Such cube root is termed the bending length, for it measures the length of fabric that will bend under its own weight to a definite extent. The stiffer'the fabric, the greater is the length necessary to ensure bending sufiiciently, so that a high value of corresponds to a stiff fabric and a low value of c-corresponds to a pliant fabric. 1

' (2) The flexuml rigidity, G.While thebending'length is the measure of stiifness that determines the draping qualities of the fabric, the fiexural rigidity is a measure of the stiffness as appreciated by the fingers-the resistance to bending. It is the couple on either end of a strip of unit width bent into unit curvature-'-the pair of forces acting in opposite directions that would be appreciated as a pressure on the skin if such a bent strip were held between the finger and thumb. Thus the evaluation of flexural rigiditycan be derived from the bending length,

' the weight and the area of the specimen.

(3) Other quantities that are pertinentto the precis ing modulus, compression modulus, density and extensibility.

Instruments heretofore employed for determining thev stiffness of a fabric specimen include the Clark paper softmess-stiffness tester, the Tinius Olsen stiffness tester, the

Patented Nov. 18, 1958 be determined; the results are empirical and have little Pierce stiffness tester, and the bending-length tester decribed in The Textile Research Journal issues of August significance as to measurements of fabric hang or draping characteristics; and fabric curl cannot be measured. The Tinius Olsen tester does not measure the draping or curling characteristics of fabrics, is primarily a device for measuring the fiexural rigidity of plastics and thin sheet metal and is therefore not sensitive enough for many fabrics, is inordinately expensive, and, being motor-driven,

is impractical for use in low-temperature measurements Pierce uses the method based on the determination of the. angle of bend for a fixed length of overhangand thus is complicated to use, since no single standard fixed length is suitable for the general range of textile fabrics. The use of a variable angle by Pierce introduces inaccuracies and prevents comparison because sensitivity varies with the magnitude of the angle and because the resistance to bending of a fabric is not the same at all-angles. addition, Pierce cannot be employed toshowthe difference in stiffness between the face and the back of a fabric specimen because of inaccuracies due to curling, nor can 1 Pierce be used to measure curl. The bending-length tester described in the Journals cited is too crude to give accuracy or reproducibility, and does not overcome the difficulties of curling and twisting.

The principal object of this invention is to measure simply, quickly and accurately the bending length and flexural rigidity of a fabric specimen.

Another object is to provide a cantilever-type fabric bending-length and fleXural-rigidity tester. 'i

A further object is to provide facile and accurate means to measure the stiifness and curling characteristics of fabrics.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a perspective view of a cantilever-type fabric bending-length and flexural-rigidity tester, showing one embodiment of the invention;

Fig. 2 is a perspective view of the device of Fig. 1, showing the clamp element and the fabric specimen in another position;

I Figs. 3 and 5 are perspective views of modified forms of the device of Fig. 1; and

Fig. 4 is a perspective view of the device of Fig. 3, the parts being in a relative position diifering from that of Fig. 3, and

Fig. 6 is a view in elevation and partly in section of 15, the plane of said wall 15 defining an angle of 43 with the plane of the base of said block. It is usual and sometimes convenient to have platform 13 horizontal but obviously it is not necessary. The 43 angle is also a matter of convenience. As explained hereinafter, when the angle between the plane of the wall and the plane of the block base is 43, the bending length 0 is one-half of the overhanging length of the sample when it is in the position ofFig. 2'. However, other angles can be used, in which case the device is calibrated with materials. the bending length of which is known. Ruler guide 17 extends substantially the length of said platform 13 and is secured thereon by sorews.19.. A rectangulan'wi'ndow or? opening 21 in wall: 15 is of sufiicient width: and length to permit" unimpeded. passage of the fabric specimen therethrouglr, ashereinaften described. I

An elongated rigid bar 23, upon which is secured aweight 25', is provided. The fabric-specimen Clamp'GOtn prises? a leaf spring 27' secured upon and encasing. one end of. said bar or plate. An upstanding ean 29 of said spring 27 facilitates the operation ofpushing bar 23 along platform 13 and retaining said bar in engagement with the edge 31 of ruler 17. A second ear 33:extends la-terally from the nether leg of spring 27, whereby said leg can be depressed to permit insertion ofa portion of a fabric specimen 35 betweensaid leg and neither face of said bar 23; with the free end of said: specimen aligned withthe end 39 of'saidbar.

To assure reproductibility of'results, the elements above described are so proportioned that the end 39 of bar 23 is substantially flush with wall 15 when marker 37 is aligned with the Zero point on" the ruler 17, and the fabric specimen-'35 to be-tested is coextensive with that portion of the bar 23" that lies between the marker 37 and the end 39.

In the operation of" the apparatus above described, the block is placedso thatthe platform is at eye height. The fabric specimen to be tested is then placed lengthwise in the clamp so that the free end of the specimen is exactly even with the end 39', with the surface to be tested being 'theupper surface; The clamp and the specimen are then placed on the stand so that the reference marker 37 coincides with the zero point on the ruler, as shown in Fig. 1. The weight 25' serves to hold the sample downto the platform.

The clamp, together with the specimen, is moved slowly along the platform against the ruler until the free end of the sample drops to the 43 slope when viewed parallel to the surface otthe slope. A reading canthen be taken from the ruler, the marker 37. indicating the distance of traverse along said ruler. This reading. is the length of the unsupported sample, or two times thecharacteristic bending length of the specimen. The provision of the rectangular window or opening 21 permits the measurement of the bending length of fabrics that twist when out into strips, a reading being taken for such samples when the midpoint of the twisted bottom edge has. dropped to the 43 slope when viewed parallel to the surface of said slope.

A more accurate method is to read the projections when the lower downturned corner and. the higher upturned corner coincides with-the 43 slope andto then take an average of the. two readings. A value for curl is obtained by taking the difference between the two readings.

The significance of the provision of'a 43 slope can be appreciated by consideration of the reduction tables derived by F. T. Pierce and reported in the Journal of the Textile Institute; Transactions, September 1930. In the. analysis by Pierce for the rectangular cantilever method, it is stated that the length. overhangingcan be adjusted to a suitable value 1, and the angular deflection 0 observed when the bending length C=1 f (0), where cos 0.50 1 (8 tan 0 3 The derived table of values of 71(0) shows that at 43 the resultant is .500, so that the bending lengthor drape stiffness c can be defined as one-half of the overhanging length of the sample when it reaches the 43 slope and flex stiffness (combining drape stiffness and fabric weight) can be obtained from the equation Flex stiffness (G) =6 w 0.482 X where c=drape stiffness In the practice of the method with the device disclosed, it is preferable to test a number of specimens from each unit of product in each of the warp and filling directions. The drape and flex stiffness or the curl of the unit of product will then-be. the average of the. results obtained from the specimens tested in each of the warp and filling directions.

In the device shownin Figs. 3 and. 4. the block 11 is movable, in guideway 41, relative to a sample, which is held fixed by any'suitable means; such as yoke 45 against which the end of the sample seats. The upper surface of the block is a platform 13 for the sample. The yoke stands on the guideway and the block moves through the yoke. As in- Fig. 1, an end of the block is at an angle, greater than with the top of the block, i. e., with platform 13 and is a sloping wall 15. It, too, can have a window 21. There are means for assuring that some portion of the specimen is in contact with the upper edge of wall 15 and at that edge is in a horizontal position While the wall and the specimen are moved relatively to each other and in such contact that the plane of the specimen at the' saidedge is parallel with the plane of platform 13. For example this can be a plate 43 hinged to yoke 45 and adapted to be laid down on top of the specimen (see Fig. 3) or it can comprise, say, a pair of retaining fingers on theplatform. 13' at the edge of the wall 15. The. total friction between the plate and the specimerr should be greater than between the specimen and' the: platform 13. There are scale indicia for measuring the. relative motion of the. block and the securing means. A scale of inches 37 can be marked 011 on the side of. the block adjacent the guideway 41 and an index 37"can be marked on the guideway as shown or the scale can, be on theguideway and the-index on the block or the scale can be on the block adjacent an index on the clamp.

The method of testingwith the device of Figs. 3 and 4 is substantially the same as that described above. The specimen is laid on platform 13 with one end abuttingyoke 45. The other. end of the specimen is-held against the top. edge of the sloping wall either by plate 43 or fingers 47 or other suitable means. The surface of the specimen to be tested is the upper surface. Any means can be used. tomeasure the movement of the block with respect to the specimen. There may be a scale of inches on the side of the block, the zero of which can be set at marker 37' when the end of the specimen is at the top edge of the sloping wall. As before, the relative motion of the block and specimen is stopped when the hanging edge of the specimen is aligned. with the sloping wall of the block. The motion is the motion of the block. In the case of a very sheer fabric or fabric that tends to accumulate electric charge a reverse motion can be used with any of the devices, in which case the specimen originally extends down into the opening 21 and the block is moved in the reverse direction until the specimen. reaches the, final position. in which the free end thereof is aligned with the sloping wall.

Fig. 5 showsa device similar to that of Fig. 1. It. has anextension of the sloping wall 15. The extension, when in extended position, is coplanar with wall 15 and has a window 121 similar to window 21. The extension is used for testing stiffer material's. When as used, the block 11 is placed on a table with an extension projecting over the edge of the table. When it is not to be used, it is swung around axle 47 and seated in a recess 49' in the base of block 11.

- In the device shown in Fig. 6, 15 is a sloping wall set at an angle, say, of 41.5" with the horizontal. upper end of the'wallis a pair of rollers- 50. The hori- At this I zontal axes of the rollers are in the same vertical plane. There is a platform 13 adapted to support a test specimen 35 in a position to be fed horizontally between the rollers. Means (not shown) drive one or both of the rollers. An index 137 on one roller indicates the angular displacement of the roller and hence the amount of the specimen that has passed through from the time the forward edge of the specimen entered between the rollers until' it has reached the surface of wall 15. There can be a scale of inches at the edge of a face of the roller. The rollers are positioned so that the portion of the specimen between them intersects the plane of the wall 15. In place of the platform there can be a pair of idling rollers positioned to have the specimen pass between them and continue horizontally toward and between rollers 50. The platform can be omitted, in which case rollers 50 should be of such size and softness that when they are pressed together, by their own weight or other pressure, the specimen between them lies in a horizontal plane. The operation of this device is similar to those previously described herein.

Obviously many modifications and variations of the present invention are possible in the light of the above teaching-s. It is therefore to be understood that within the scope of the appended claims the invention can be practiced otherwise than as specifically described.

I claim:

1. A cantilever-type fabric tester comprising a block having an upper plane horizontal platform and a depending outwardly sloping wall forming an end face of said block, said wall having a fabric specimen-receiving slot therein, a guide having scale indicia along its length, said guide being secured upon said platform, a bar member having a plane nether side and carrying a clamp adapted to secure a portion of a specimen against said nether side of said bar member, said bar member being mounted slidably for movement over said platform along said guide, means to push said bar member carried by said clamp, means to depress said clamp carried by said clamp, a weight secured upon the upper face of said bar member to retain a portion of said specimen against said platform, there being a reference marker on said bar to indicate the distance of travel of said bar relative to said indicia of said guide.

2. A cantilever-type fabric tester comprising a block having an upper plane horizontal platform and a depending outwardly sloping wall forming an end face of said block and defining an angle of 43 with the horizontal, said wall having a fabric specimen receiving slot therein, a guide having scale indicia along its length, said guide being secured upon said platform, a bar member having a plane nether face and carrying a clamp adpated to secure a portion of a specimen against said nether face of said bar member, said bar member being mounted slidably for movement over said platform along said guide, means to push said bar member carried by said clamp, means to depress said clamp carried by said clamp, a weight secured upon the upper face of said bar member to retain a portion of said specimen against said platform, there being a reference marker on said bar to indicate the distance of travel of said bar relative to said indicia of said guide.

3. A cantilever-type fabric tester comprising a platform, a guide secured on said platform, a depending sloping wall at one end of said platform, said wall having a fabric-specimen receiving slot, and a fabric-specimen clamp mounted slidably on said platform for movement along said guide and partly over said wall, there being scale indicia on said guide adapted to measure the distance of travel of said clamp relative to said guide.

4. A cantilever-type fabric tester comprising a block having an upper platform and a depending outwardly sloping wall forming an end face of said block, said wall having a fabric-specimen receiving slot, a guide secured on said platform, and a clamp adapted to secure a portion of a fabric specimen, said clamp being mounted slidably for movement along said guide and partly over said wall, there being indicia on said guide and clamp to measure the distance of travel of said clamp relative to said guide.

5. A cantilever-type fabric tester comprising a block having an upper platform and a depending sloping wall forming an end face of said block, said wall having a fabric-specimen receiving slot, a guide having scale indicia secured on said platform, a bar member carrying a clamp adapted to secure a portion of a specimen against the nether side of said bar member, said bar member being mounted slidably for movement over said platform along said guide, said bar member having a reference marker thereon to indicate the distance of travel of said bar member relative to said indicia of said guide.

6. A cantilever-type fabric tester comprising a block having a plane upper platform and a depending outwardly sloping wall forming an end face of said block, said wall having a fabric specimen receiving slot therein, a guide having scale indicia along its length, said guide being secured on said platform, a bar member having a plane nether side and carrying a clamp adapted to secure a portion of a specimen against the nether side of said bar member, said bar member being mounted slidably for movement over said platform along said guide, means to push said bar member carried by said clamp, means to depress said clamp carried by said clamp, there being a reference marker on said bar member to indicate the distance of travel of said bar relative to said indicia of said guide.

7. A cantilever-type fabric tester comprising means for securing one end of a test specimen, a platform adapted to support said securing means and a test specimen so secured, pressure means carried by said securing means for maintaining said specimen in contact with said platform, a depending sloping wall defining one end of said platform, said wall having a specimen receiving slot, said platform and said securing means being movable relative to each other, whereby a portion of such specimen is adapted to be projected over said wall.

8. A cantilever-type fabric tester comprising a sloping wall having a fabric-specimen receiving slot, and means secured to said wall for supporting a test specimen horizontally at a line co-planar with said wall, and for moving a free end of said specimen, so supported, into projected position over said wall whereby said free end is adapted to move partly into said slot.

9. A cantilever-type fabric tester comprising a sloping wall having a fabric-specimen receiving slot, and means secured to said wall for supporting a test specimen horizontally at a line co-planar with said wall, and means for moving a free end of said specimen, so supported, into projected position over said wall whereby said specimen is adapted to move partly into said slot, said means for supporting and said means for moving comprising a pair of rollers.

10. A cantilever-type fabric tester comprising a sloping wall having a fabric-specimen receiving slot, and means secured to said wall for supporting a test specimen horizontally at a line co-planar with said wall, and for moving a free end of said specimen, so supported, into projected position over said wall whereby said specimen is adapted to move partly into said slot.

Chu: Textile Research Journal, August 1950, vol. XX, No. 8, pp. 547-548.

Pierce: Journal of the Textile Institute, September 1930, vol. 21, No. 9, pp. T380, T381 and Fig. 142. 

